The present invention relates to fuel injectors. More particularly, the invention relates to methods and devices used to control the actuation of fuel injectors.
Modem internal combustion engines rely on electronically controlled fuel injection systems. Mechanical injectors spray or otherwise dispense fuel within the combustion chamber(s) of the engine at specific times. The timing of fuel dispensing and the amount of fuel dispensed affects engine performance in a myriad of ways. While systems have been developed to control fuel injectors, these systems suffer from several deficiencies.
As is known, a fuel injector has an electromagnetic coil that is used to open and close a fuel-metering valve to control the flow of fuel into the engine. In most conventional fuel systems, the drive signal delivered to the coil is an amplified square wave. The square wave deteriorates slightly as it is amplified and run through the coil. Thus, the signal delivered to the fuel injector is not a true square wave. One deficiency in modem systems is that distorted square wave signals cause the armature to forcefully drive the valve into end stops positioned at either end of the path of travel of the valve. When the valve contacts the stops, the valve bounces. This generates an unpleasant noise and excessive wear of the valve and stops.
In light of the noted noise and wear problems of present fuel injection systems, there is a need for an improved fuel injection system that eliminates or reduces valve or armature bounce.
The present invention includes a fuel injector control system that modifies the control signal sent to the electromagnetic coil of a fuel injector. The control system has a microprocessor or other programmable device that delivers an output signal to an amplifying circuit such as a power transistor. The microprocessor modifies the control signal by notching or stepping the signal at times that correspond to the opening and closing of the injector valve. The notches in the signal help eliminate vibrations in the fuel injector caused by the impact of the valve contacting the stops within the injector. The microprocessor adjusts the notching of the drive signal by monitoring the electromagnetic characteristics of the fuel injector.
The invention also provides a method of driving a fuel injector that includes, sending a drive signal to a fuel injector, sensing whether the armature contacts the body of the fuel injector, running the injector with the drive signal if no contact is detected, and upon sensing contact between the armature and the body, modifying the drive signal. As noted, the drive signal is modified by notching or stepping the drive signal. The modified drive signal is reapplied to the fuel injector and the system then senses whether the armature contacts the body of the fuel injector when driven by the modified drive signal. The system continues to modify the signal until no contact between the armature and the body is detected. The injector is then run with the modified signal.
As is apparent from the above, it is an advantage of the present invention to provide a method and system for controlling a fuel injector. Other features and advantages of the present invention will become apparent by consideration of the detailed description and accompanying drawings.